This invention relates to fire escape, ladder, or scaffold. More specifically, platform with ladder as support. More specifically to standoffs: device including means to su ort the ladder away from the surface against which it leans or rests.
Ladders of issue include one-fold A-frame folding ladders, straight ladders (slide or unfolding), and scaffold ladders, including pivotally connected ladders. Many such ladders are for building, repairing, painting and the like of vertical walls/surfaces, and surfaces near such vertical surfaces. Accessories for ladders include trays, (for supplies) and stabilizing supports.
Each ladder type has disadvantages. One-fold folding A-frame ladders have limited height, need sure footing for all four legs, & need a substantially level surface to correctly unfold its A frame. They have nearly no room for painting supplies and the like on the ladder platform. Inside floors provide for such secure footing, but outside ground can be uneven (like 2 legs on the sidewalk and two legs in the garden area abutting/near the building.
Straight ladders have disadvantages. To work on a vertical surface a user steps many steps down form the top of a ladder to be at a distance horizontally away from the vertical surface. Prior Art FIG. 1a is a sketch of a user painting on a ladder, front view. It shows the user cannot work much directly in front of them much because the ladder is in the way. By painting to a user's side, a user counterbalances themselves sideways against the ladder, which is a stressful position for a user, can dig into the wood by the sideways rubbing of the ladder's top end, and can unbalance the ladder. (It's an OSH “don't”). [“OSH” in this Specification refers to U.S. Federal law entitled Occupational Safety and Health Act of 1970 (OSH Act)] Ladder-top friction pads and accessory side supports are available to sideways-stabilize a ladder. But side supports make the ladder more top-heavy, harder to balance when moving, can't get close to corners, take time to attach, and still provide no place to support supplies near ladder top end.
A straight ladder is often 16 inches wide, and a user's arm can extend sideways an average of 2 to 2.5 feet, plus brush length. Most users paint with their favored hand, to do a good job. Prior Art FIG. 1b is a sketch of a user painting on a ladder, top view. It shows that, because the ladder crosses in front of a user's chest, it is nearly impossible to paint on the users non-favored side of the ladder. That means that a straight ladder would have to be re-positioned every one to 1.5 feet sideways. This becomes more involved when a user is working on a roof-pitched vertical surface, where the needed ladder height changes with the roof pitch height.
Prior Art FIG. 1c shows right hand side view of a user moving a ladder. (In this Specification, RHS is the abbreviation for right hands side.) Prior Art FIG. 1f shows front view of a user moving a straight ladder. Phantom lines show a prior art standoff. As depicted in drawings, straight ladders are tall such that most of their weight is above a persons arm level. The weight above arm/grabbing level often includes a ladder-portion overlap. When picked up and moved, straight ladders must be levered and balanced into place. This can be dangerous. Moving such a ladder can damage vertical surfaces when unbalanced, or the ladder can fall or be dropped before it is secured in place. Sliding a ladder vertically taller, either by hand or mechanism, still has the balancing problem to secure against a vertical surface. Additionally, any tray for supplies would best be attached after the ladder is erected, to prevent a more top-heavy condition when moving. So not only must a straight ladder be moved often because a user can only paint to the side, but any tray may need to be removed with every move. Prior art trays, often flat, provide little security against spillage or dropping if accidentally bumped. This often means limited supplies near the top of a ladder. Without much security for supplies, many users, doing more than just painting, haul supplies up and down the ladder several trips before ladder must be moved. Climbing up and down a ladder is not fun, always includes the possibility of a potential fall, and is time consuming. Standoffs (phantom lines in Prior Art FIG. 1f), hold the ladder back from the vertical surface like 10″, but is 4′ wide, so cannot mount everywhere, like close to windows, and roof pitch. Standoffs also cannot get right to the corner of a house (like for painting corner overhangs).
Straight ladders with and without standoffs have nowhere to mount a paint can or tool. When tools or paint cans are hung off the side of the ladder, that places an unbalanced weight sideways on the top part of the ladder. Both leaning to the side and having weight to one side is a common cause of a user on a ladder falling down sideways.
On exterior vertical surfaces, may buildings have eves which must be worked on. As eves overhang the vertical surfaces, a straight ladder is often not tall enough for a user to work on the eves without leaning back. This is shown in Prior Art FIG. 1d is a sketch of a user painting a truss, side view. Many hold onto an eve structure, like an overhead truss. This is because one must step farther down the ladder to reach farther away from the supporting vertical surface. Leaning back can be dangerous. Holding on to an above-head structure, like a truss, is not a secure hold. Such a lean-back can cause a user to fall-fall from a high location. A user often puts the straight ladder in an almost vertical position to reach as high as possible. An already near-vertical ladder can lift off the vertical surface, and take a user down. Leaning a straight ladder against the gutters also does not provide access to working on the eves.
A ladder's force against a vertical surface, or horizontally-supporting structure, is calculated by equations for equilibrium. Referring to Prior Art FIG. 1e, a force analogy diagram:ΣFX=0=NA−μNB ΣFY=0=NA=μNA−#ΣMA=0=−#(0.5L cos Ø)+NB(L cos Ø)−μNB(12 sin Ø)OSH recommends footing the ladder 1 meter out for every 4 meters tall. Footing a ladder means placing/weighting the lower end of the ladder on substantially horizontal ground.
Exterior work has the benefit of ground and cement, both highly frictional surfaces (μNB).
ANSI does bottom slip test for a leaning/straight ladder. Angle 75.5°, load (200-300#)—3rd step down, plywood floor & vertical surface, 50# pull 1″ above test surface. (75.5° is the 4 up to one out angle of lean.) A-frame folding ladders are not known to currently be ANSI specified for leaning against a vertical surface.
Pivotally-connected ladders have problems. U.S. Pat. No. 4,216,844 entitled FITTING FOR JOINTS OF LADDER SECTIONS, granted Aug. 12, 1980, by Klafs is an example of the locking joints that connect ladder sections for multi-ladders. The locking joints on these ladders must be fully and properly secured so they do not collapse, especially in use. The joints can easily rust, some say in just one year. (Likely because soft plating on joint parts rubs off when joints are rotated, which is aggravated by frequent use.) This rusting can prevent the joints from locking and/or unlocking. It can keep the ladder from unfolding or from fully folding the ladder back. Some users lay the ladder on the floor, stand on one section, and try to pry another section open or press it closed. A user's fingers can get cut up on the joints while trying to adjust/lock/unlock the joints or fold or unfold the ladder. When not properly locked, a ladder can collapse causing a fall. Many users find these problems frustrating enough to discontinue using such a ladder. (A homeowner who has fewer projects more often chooses a ladder that is simpler to use). Some pivotally-connected ladders may be assembled like an upside-down italic capital L, such that the ladder's top end is away from the vertical surface, which is desirous for working on trusses. Prior Art FIG. 2 is a sketch of a user on such an L-formed multi-ladder. This position places a substantial stress on the small-diameter joints. If a collapse occurs, a user could crash against the surface on which they work, then fall. Multi-ladders can have four 3′ or 4′ segments. A depicted 12′ ladder could be made 9′ tall and would stand 3′ away from the vertical surface. This distance can not be made smaller. To the average eye, this L position does not look safe. As most user's arm is 2′ to 2.5′ long, the user cannot reach the vertical surface against which the ladder rests without leaning over, which adds further stress to the joints, and is not a comfortable position. Commonly, such an angle would be supported by a cross-bar. Such a bar is shown as notation 10 in U.S. Pat. No. 4,121,692 entitled LADDER TRAY, granted Oct. 24, 1978, by Morawski, FIG. 1; and as support 14 in FIG. 1 of U.S. Pat. No. 4,460,063 entitled STEP-LADDER WORK BENCH, granted Jul. 17, 1984, by Casada. A pivotally-connected ladder positioned like in Prior Art FIG. 2 has platform rungs (steps) which do not provide a surface by themselves for supplies. If a board were put over the horizontal rungs, supplies it would place additional stress on the joints, and still have no security from being bumped off.
Morawski's tray, as shown in his FIG. 2, has rubber feet 44 with a benefit detailed in specification P. 3, lines 22-32, which recites, “In order to improve the engagement between the frame 10 and the vertical surface . . . (legs with) resilient pads 44 formed of rubber . . . (are attached) so they may be replaced as they wear out”. (friction/padding benefit)
U.S. Pat. No. 5,123,620 entitled ACCESSORY CONTAINER FOR LADDER, granted Jun. 23, 1992, by Bourne is an example of a container supporting against the rear portion of the back rails of a ladder. Bourne's FIG. 3 is redrawn here as Prior Art FIG. 3a. Prior Art FIG. 3b is Bourne's FIG. 3 invention on a leaning ladder. For his container to continue to support against the rear portion of the back rail of a ladder, its top edge would dig sharply into a vertical surface. Bourne does not provide, nor have a place for any rubber feet, like Morawski's feet 44, that might protect a vertical surface if the ladder was leaned with the container in place. Bourne's container teaches away from securing a ladder a distance from a vertical surface when leaned. Bourne's FIG. 3 (Prior Art FIG. 3) supports his box at two points against an OPEN A-frame, but his invention can't support an A-frame ladder at a leaned angle, whether the ladder is open OR closed. HI invention can't support on a ladder and have the box back side flat against a vertical surface. Applicant's invention supports better than the angular support of Casada's arm braces (FIG. 1, n. 14).
Often painting requires about a one or two-foot lift before using a ladder. Some users stand on what looks like a stool, but does not meet OSHA standards to be called a stool. An example is the 16″ tall plastic SIDE TABLE #03937 by Syroco as seen on web site www.syroco.com. The surface area is a rough texture that is of benefit as a step stool but not so much as a table (rough surfaces collect dirt, and a recessed surface would better prevent slippage off a side table). Many purchasers of such items buy them to use them as a stool. They have 4 supporting feet, which is not often sure footing on outside ground which is rarely level.
Folding stools also have problems for use outside. Their small-diameter rod-like legs can sink into the ground. The stool steps are not deep, or their depth cannot be used without bumping ones chins. So the stool must be positioned just-so: away from an outside vertical surface such that one can balance on the balls of ones feet. Users may need to lean on the vertical surface they are painting. This may lead to transfer of paint or dirt between the user and the vertical surface.
Des. Pat. No. 340,773 entitled LADDER TOP, granted Oct. 26, 1993, by Bartnicki et al. shows a ladder top end with several through-and through holes for tools, and a round recessed platform portion of a size to support a quart of paint. Prior Art FIG. 4 is a sketch of his prior art ladder top end FIG. 1, top view. ladder top end holes 66, 67, and 68 are noted. These noted holes are located on the far side of the ladder top end, versus the larger two side holes which are on the ladder top end front side, closest to ladder steps.
A ladder top end surface design likely has to avoid being designed of a look to hold larger or more spillable objects than OSHA might allow. There is a narrow hook on the ladder back, of a size and shape to hang an object with a metal wire handle (plastic handles, like for spackle, don't fit on it). The only common item that could be hung from such a hook is a gallon can of paint (paint in quarts do not come with metal wire hangers). The hook is recessed into the ladder back, which allows the ladder to be leaned smoothly against a vertical surface, which shows the designer recognizes that a ladder is often leaned against a vertical surface. When a folding ladder is leaned against a vertical surface it is often leaned at an angle more severe than when opened as an A frame. This leaves the ladder top end tilted, versus being a level surface.
Many ladder manufacturers have through-and-through holes in their ladder top end. Manufacturers include Werner®, Husky®, & Green Bull™.
Prior Art FIG. 5a is a prior art plastic crate, top perspective view. Heavy-duty prior art milk crates are often of two sizes: 12″×12″ I.D. top opening and 12″×18″ I.D. top opening. Prior art plastic storage/file crates for home use are often 12.5″×14″ I.D. Crates are of average 11″ deep. Prior Art FIG. 5b is a prior art plastic crate, cross-sectional view. Top wall T and bottom wall B are substantially parallel, widening near the opening to let the core of the injection molded tool to pull out in the direction of the arrow. Often this is a 4 degree sidewall taper. The top and bottom wall are considered substantially parallel for this specification. The crate walls are made light-yet-strong substantially by spiked grid walls (like a honeycomb), perpendicular to the wall. All sections of an injection molded part must be the same thickness such that the plastic flows evenly into the mold. This is why even corners of the crate that take abuse are thin. A detail of Prior Art FIG. 5b is shown in Prior Art FIG. 5c, which shows smooth side S and spiked grids G. Plastic thicknesses are often about 2 mm., with at least some grade for ease of ejection. Prior art metal ribbon bands have also been added on a crate rim for strength. The interior surfaces of the crate are smooth so molded crates can be ejected from the tool. Smooth side S is also marked on Prior Art FIG. 5b. Prior art crates have the smooth side inside, and require the SIDES to be smooth inside in order to pull the core of the tool off the molded crate. Some prior art plastic crates are made with a percentage of glass fibers, added for strength. Plastic with glass fibers does not fill a mold well in narrow spaces, so crate walls are made thicker, requiring more plastic than a plastic crate with similar-strength grid walls. Also, glass fibers scratch the tool, reducing tool life.
The frame width near the base of prior art A-frame ladders is wider than near the top of same ladder. Most all ladders have steps/rungs 12″ apart (top of rung to top of rung). The ladder top end/platform of prior art A-frame ladders is often 13″ wide, and the top-most step/rung is one foot down. The ladder is often 14″ wide at that top step. Straight ladders are often closer to 16″ wide at the top, first cross-bar/rung (like first rung C in Prior Art FIG. 1b) is often 6″ to 9″ from the top of the ladder. Where an A-frame ladder has a top platform, aluminum and fiberglass straight ladder's top-most portions are often called end caps (notation E in Prior Art FIG. 1a). Older-style wooden straight ladders may not have any distinctive end cap, but when “end cap” is referenced, it is the uppermost portion of the ladder rails above the first cross bar. Straight or A-frame, the top of steps/rungs, or crossbars of a ladder are generally one foot down from each other. A-frame ladders often post, “do not stand above this point” on the first step down from the top platform. OSHA Quick Card Ladder safety tips states, “Do not stand on the three top rungs of a straight, single or extension ladder.”
A straight ladder often has two sections that slide apart to extend or reduce the length of the ladder. These two sections are substantially vertically parallel to each other. This can be seen in the drawing of Prior Art FIG. 1c. When an A-frame ladder is folded closed, front and back ladder sections are also substantially vertically parallel to each other. This can be seen in the closed ladder of Prior Art FIG. 3b. 
FIG. Prior Art 4a shows user with a closed prior art A-frame ladder against a surface, side view. OSHA Quick Card Ladder safety tips states, “Do not use a self-supporting ladder (e.g., step ladder) as a single ladder or in a partially closed position.” An A-frame ladder can be made to pass slip test with footing and ladder top end design. The ANSI test is where dead weight is placed on the ladder and 50 pounds of force pushes outward at the base of a ladder that is sitting on sanded plywood. The ladder should not move more than 0.25″.
A prior art cylindrical paint can has substantially an 8″ diameter.